Notices respecting New Books. 153 



ments, insertions of from 20 to 60 miles of telegraph-wire cer- 

 tainly made the needle of the multiplier go back for a few se- 

 conds, but then soon permitted it to return to its previous de- 

 flection. The resistance of the rest of the circuit amounted to 

 only about 2 miles of the same wire ; the behaviour of the per- 

 manent current-intensities which appeared in the circuit with 

 alternating resistances was just as if there existed at the surface 

 of the plates a passing resistance in comparison with which 

 40-60 miles of wire was vanishingly little. This enormous ap- 

 parent transitory resistance, however, existed only for just the 

 then present direction of the current ; if a current of the oppo- 

 site direction was called forth, no such resistance was present. 

 This holds good not only for platinum electrodes polarized by a 

 Daniell element nearly to the maximum, but also for such as have 

 been again depolarized almost to the vanishing of the polariza- 

 tion, and have thus arrived as nearly as possible at their natural 

 state. 



XIX. Notices respecting New Books. 



Treatise on Practical Solid or Descriptive Geometry : embracing 

 Orthographic Projection and Perspective or Radial Projection. By 

 ~W. Timbeell Pieece, Architect, late Lecturer on Geometrical 

 Drawing at King's College, London. With 85 Plates of Original 

 Drawings. London : Longmans, Green, and Co. 1873. 



r pHIS volume is a small quarto, consisting of the plates and a 

 -*- text of 86 pages. About two thirds of it are devoted to 

 orthographic, and the remaining third to radial projection. The 

 former part is strictly elementary, but it embraces all the points 

 which under ordinary circumstances a student wxmld wish to 

 make out. After a brief view of the projection of points and 

 lines, with a few examples, the author fairly begins the subject in 

 the second chapter, on Straight Lines and Planes, which is in 

 substance the same as the first section of the Geometric Descrip- 

 tive of Monge. It is followed by a good many applications — one 

 chapter (the third) treating of the projections of the five regular 

 solids, while the fourth shows how to determine the projections of 

 a cube from various data, and to solve a few other problems. The 

 remainder of this part of the work is mainly devoted to a number 

 of questions of intersection and tangency of a plane with cylinder, 

 cone, and sphere, and of the mutual intersection and tangency of 

 the same solids with each other ; though a few other cases are 

 given, such as the section of an annulus by a plane, and the con- 

 tact of a cone with a surface of revolution. The treatment is 

 clear and accurate ; and though the subject is not without its diffi- 

 culties, the student who brings to it a moderate acquaintance with 

 solid geometry will be able to read it without serious trouble. 

 The case is somewhat different in the second part, the subject 



